Yongkang Hu

Anisotropic Magnetoresistance Analysis of Permalloy Film Using 2-dimensional Magnetization Vector Measurement

We measured in-plane 2 dimensional magnetization vector using two pick-up coil sets and investigate the relationship between magnetization vector and anisotropic magnetoresistance. We can determine magnetization vector by measuring magnetic moment in x and y direction simultaneously. As the uniaxial magnetic anisotropy of permalloy film increases, magnetoresistance approaches the expectation which is calculated from the angle between current vector and magnetization vector. Magnetoresistance ratio is linearly proportional to the y moment magnitude which is parallel to the current direction

Temperature Dependence of Exchange Coupling on Magnetic funnel Junctions

Magnetic Tunnel Junctions (MTJs) were fabricated on thermally oxidized Si (100) wafers using DC magnetron sputtering. The film structures were Ta(50 Å)/Cu(100 Å)/Ta(50 Å)/Ni_(80)Fe_(20)(20 Å)/Cu(50 Å)/Mn_(75)Ir_(25)(100 Å)/Co_(70)Fe_(30)(25 Å)/Al-O(15 Å)/Co_(70)Fe_(30)(25 Å)/Ni_(80)Fe_(20)(t)/Ta(50 Å), with t = 0 Å, 100 and 1000 Å, respectively. X-ray diffraction has shown improvement of (111) texture of IrMn₃ and Cu by annealing. The exchange-biased energy is almost inversely proportional to temperature. The difference between the coercivity Hc and the exchange biased field H_E for t = 0 Å sample is smaller than that for t = 1000 Å. For the pinned layer, the decreasing rate of the coercivity with the temperature is higher compared to that of the exchange field, but variation of Hc is similar to that of the exchange field for free layer.